In this article we have developed an analytical model for Tri gate Metal oxide semiconductor field effect transistor (MOSFET) by including quantum effects. The coupled Schrödinger and Poisson’s equation is solved using variational approach to develop an analytical quantum model. An analytical model for charge centroid is obtained and then inversion charge model is developed with quantum effects by means of oxide capacitance for different channel thickness and gate oxide thickness. The compact model is shown to reproduce transfer characteristics, transconductance and C-V curve of tri gate MOSFET using the model. The modeled results are then compared to the simulated results. The comparison shows the accuracy of the proposed model.